Systems, methods, and apparatus for operation of dual fuel engines

ABSTRACT

Systems, methods and apparatus for controlling operation of dual fuel engines are disclosed that regulate the fuelling amounts provided by a first fuel and a second fuel during operation of the engine. The first fuel can be a liquid fuel and the second fuel can be a gaseous fuel. The fuelling amounts are controlled to improve operational outcomes of the duel fuel engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International Patent App.No. PCT/US2015/59012 filed on Nov. 4, 2015, claims priority to and thebenefit of the filing date of U.S. Provisional Application Ser. No.62/074,989 filed on Nov. 4, 2014 and U.S. Provisional Application Ser.No. 62/101,422 filed on Jan. 9, 2015, each of which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to dual fuel internal combustionengines, and more particularly is concerned with systems and methods forfuelling control of a dual fuel internal combustion engine.

BACKGROUND

An example dual fuel engine is an engine that includes a first fuelsource that is utilized as the sole fuel source during certain operatingconditions and a second fuel source that is integrated with the firstfuel source at other operating conditions. In certain applications, thefirst fuel source is a diesel fuel and the second fuel source is naturalgas. The diesel fuel provides, in some cases, the initial, low loadlevels of operation and is used for ignition for the natural gas athigher load operations. The substitution of natural gas for diesel fuelreduces the costs of operating the engine, particularly when the engineis employed at locations where natural gas is abundant or available atlow cost.

When the engine is operating in dual fuel mode, natural gas fuel isintroduced into the intake system. The air and natural gas mixture fromthe intake is drawn into the cylinder, just as it would be in aspark-ignited engine, but the air-to-fuel ratio of the charge mixturecan be much leaner than a typical spark-ignited engine. Diesel fuel isinjected near the end of the compression stroke, just as it would be ina traditional compression-ignition engine. The diesel fuel is ignited byenergy compression heating of the charge and the energy released fromcombustion of the diesel fuel causes the natural gas to burn. A dualfuel engine can operate either entirely on diesel fuel or on thesubstitution mixture of diesel and natural gas, but generally cannotoperate on natural gas alone except where an auxiliary ignition sourceis provided to the cylinder.

While some control strategies compensate for natural gas qualityvariations by controlling gas substitution to obtain a desiredair-to-fuel ratio, such approaches are limited by the ability toaccurately measure and/or predict air flow rates, fuel properties, andsometimes gaseous fuel flow rates. Therefore, further contributions inoperation and control of dual fuel engines are needed.

SUMMARY

Unique systems, methods and apparatus for controlling operation of dualfuel engines are disclosed that regulate the fuelling amounts providedby a first fuel and a second fuel during operation of the engine. In oneembodiment, the first fuel is a liquid fuel and the second fuel is agaseous fuel. The fuelling amounts are controlled to improve operationaloutcomes of the engine. In another embodiment, systems, methods andapparatus are disclosed for dual fuel substitution rate optimization inthe presence of engine knock.

Another exemplary embodiment is a system comprising a dual-fuel enginestructured to selectably combust a combination of liquid fuel injectedinto a cylinder of the engine and gaseous fuel provided to the cylinder;and a controller structured to control a substitution parameter forsubstitution of the gaseous fuel for the liquid fuel based uponinformation of an engine load, an intake manifold temperature, and agaseous fuel quality. The controller is further structured to determinethe gaseous fuel quality based upon at least one of a first parameterinput by an operator and a second parameter determined by thecontroller.

This summary is provided to introduce a selection of concepts that arefurther described below in the illustrative embodiments. This summary isnot intended to identify key or essential features of the claimedsubject matter, nor is it intended to be used as an aid in limiting thescope of the claimed subject matter. Further embodiments, forms,objects, features, advantages, aspects, and benefits shall becomeapparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a portion of an internalcombustion engine system with a dual fuel system.

FIG. 2 is another schematic illustration of a part of the internalcombustion engine system of FIG. 1 showing various embodiments of a dualfueling system.

FIG. 3 is a schematic of a control apparatus for duel fuel operation ofan internal combustion engine.

FIG. 4 is a flow diagram of a procedure for duel fuel operation of aninternal combustion engine.

FIG. 5 is a schematic of another embodiment control apparatus for duelfuel operation of an internal combustion engine.

FIG. 6A is a flow diagram of another embodiment procedures for duel fueloperation of an internal combustion engine.

FIG. 6B a flow diagram of a further embodiment procedure for duel fueloperation of an internal combustion engine.

FIG. 7 is a schematic of another embodiment control apparatus for duelfuel operation of an internal combustion engine.

FIG. 8 is a flow diagram of another embodiment procedures for duel fueloperation of an internal combustion engine.

FIG. 9 is a schematic of another embodiment control apparatus for duelfuel operation of an internal combustion engine.

FIG. 10 is a flow diagram of another embodiment procedures for duel fueloperation of an internal combustion engine.

FIG. 11 is a schematic of another embodiment control apparatus for duelfuel operation of an internal combustion engine.

FIG. 12 is a schematic of another embodiment control apparatus for duelfuel operation of an internal combustion engine.

FIG. 13 is a flow diagram of an exemplary controls process.

FIGS. 14-16 are block diagrams of exemplary controls apparatuses.

FIG. 17 is a graph illustrating a sequence of knock control eventsduring a startup with 50 methane number (MN) gaseous fuel.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, any alterations and further modificationsin the illustrated embodiments, and any further applications of theprinciples of the invention as illustrated therein as would normallyoccur to one skilled in the art to which the invention relates arecontemplated herein.

With reference to FIGS. 1 and 2, an internal combustion engine system 20is illustrated in schematic form. A fueling system 21 (FIG. 2) is alsoshown in schematic form that is operable with internal combustion enginesystem 20 to provide fueling for a dual fuel engine 30 from a first fuelsource 102 and a second fuel source 104. Internal combustion enginesystem 20 includes dual fuel engine 30 connected with an intake system22 for providing a charge flow to engine 30 and an exhaust system 24 foroutput of exhaust gases. In certain embodiments, the duel fuel engine 30includes a lean combustion engine such as a diesel cycle engine thatuses a primary or first fuel that is a liquid fuel such as diesel fueland a secondary or second fuel that is a gaseous fuel such as naturalgas. The second fuel can be, for example, natural gas, bio-gas,commercially available gas, methane, ethane, propane (LPG), butane,ethanol, producer gas, field gas, nominally treated field gas, well gas,nominally treated well gas, liquefied natural gas (LNG), compressednatural gas, landfill gas, condensate, coal-bed methane (CBM), liquidfuels that are readily vaporized (such as gasoline), and mixtures ofthese. However, other types of first and second fuels are not precluded,such as any suitable liquid fuel and gaseous fuel. In certainembodiments, the first fuel is a fuel suitable for lean burning, and thesecond fuel is a fuel that utilizes stoichiometric ornear-stoichiometric combustion except when combined with the first fuelduring a dual fueling operation. In the illustrated embodiment, the dualfuel engine 30 includes six cylinders 31 a-31 f in an in-linearrangement. However, the number of cylinders (collectively referred toas cylinders 31) may be any number, and the arrangement of cylinders 31may be any arrangement, and is not limited to the number and arrangementshown in FIG. 1.

Dual fuel engine 30 includes an engine block 70 that at least partiallydefines the cylinders 31 a, 31 b, 31 c, 31 d, 31 e, 31 f (collectivelyreferred to as cylinders 31.) A plurality of pistons (not shown) may beslidably disposed within respective ones of the cylinders 31 toreciprocate between a top-dead-center position and a bottom-dead-centerposition. Each of the cylinders 31, its respective piston, and thecylinder head form a combustion chamber. In the illustrated embodiment,engine 30 includes six such combustion chambers. However, it iscontemplated that engine 30 may include a greater or lesser number ofcylinders and combustion chambers and that cylinders and combustionchambers may be disposed in an “in-line” configuration, a “V”configuration, or in any other suitable configuration.

In one embodiment, dual fuel engine 30 is a four stroke engine. That is,for each complete engine cycle (i.e., for every two full crankshaftrotations), each piston of each cylinder 31 moves through an intakestroke, a compression stroke, a combustion or power stroke, and anexhaust stroke. Thus, during each complete cycle for the depicted sixcylinder engine, there are six strokes during which air is drawn intoindividual combustion chambers from intake supply conduit 26 and sixstrokes during which exhaust gas is supplied to exhaust manifold 32.

The dual fuel engine 30 includes cylinders 31 connected to the intakesystem 22 to receive a charge flow and connected to exhaust system 24 torelease exhaust gases produced by combustion of the first and/or secondfuels. Exhaust system 24 may provide exhaust gases to a turbocharger 46,although a turbocharger is not required. In still other embodiments,multiple turbochargers are included to provide high pressure and lowpressure turbocharging stages that compress the intake flow.

Furthermore, exhaust system 24 can be connected to intake system 22 withone or both of a high pressure exhaust gas recirculation (EGR) system 51and a low pressure EGR system 60. EGR systems 51, 60 may include acooler 52, 62 and bypass 54, 64, respectively. In other embodiments, oneor both of EGR systems 51, 60 are not provided. When provided, EGRsystem(s) 51, 60 provide exhaust gas recirculation to engine 30 incertain operating conditions. In any EGR arrangement during at leastcertain operating conditions, at least a portion the exhaust output ofcylinder(s) 31 is recirculated to the engine intake system 22. In thehigh pressure EGR system 51, the exhaust gas from the cylinder(s) 31takes off from exhaust system 24 upstream of turbine 48 of turbocharger46 and combines with intake flow at a position downstream of compressor50 of turbocharger 46 and upstream of an intake manifold 28 of engine30. In the low pressure EGR system 60, the exhaust gas from thecylinder(s) 31 a-31 f takes off from exhaust system 24 downstream ofturbine 48 of turbocharger 46 and combines with intake flow at aposition upstream of compressor 50 of turbocharger 46. The recirculatedexhaust gas may combine with the intake gases in a mixer (not shown) ofintake system 22 or by any other arrangement. In certain embodiments,the recirculated exhaust gas returns to the intake manifold 28 directly.

Intake system 22 includes one or more inlet supply conduits 26 connectedto an engine intake manifold 28, which distributes the charge flow tocylinders 31 of engine 30. Exhaust system 24 is also coupled to engine30 with an engine exhaust manifold 32. Exhaust system 24 includes anexhaust conduit 34 extending from exhaust manifold 32 to an exhaustvalve. In the illustrated embodiment, exhaust conduit 34 extends toturbine 48 of turbocharger 46. Turbine 48 includes a valve such ascontrollable wastegate 70 or other suitable bypass that is operable toselectively bypass at least a portion of the exhaust flow from turbine48 to reduce boost pressure and engine torque under certain operatingconditions. In another embodiment, turbine 48 is a variable geometryturbine with a size-controllable inlet opening. In other embodiments,the exhaust valve is an exhaust throttle and/or wastegate. Whilespecific examples have been discussed, no particular form of intake orexhaust control valving is required, nor is the use of the sameprecluded.

An aftertreatment system 80 can be connected with an outlet conduit 68.The aftertreatment system 80 may include, for example, oxidation devices(DOC), particulate removing devices (DPF, CDPF), constituent absorbersor reducers (SCR, AMOX, LNT), reductant systems, and other components ifdesired.

In one embodiment, exhaust conduit 34 is flow coupled to exhaustmanifold 32, and may also include one or more intermediate flowpassages, conduits or other structures. Exhaust conduit 34 extends toturbine 48 of turbocharger 46. Turbocharger 46 may be any suitableturbocharger known in the art, including fixed-geometry turbocharger,variable-geometry turbine turbochargers and waste-gated turbochargers.Turbocharger 46 may also include multiple turbochargers. Turbine 48 isconnected via a shaft 49 to compressor 50 that is flow coupled to inletsupply conduit 26.

Compressor 50 receives fresh air flow from intake air supply conduit 23.Second fuel source 104 may also be flow coupled at or upstream of theinlet to compressor 50 or downstream of compressor 50, as discussedfurther below. Intake system 22 may further include a compressor bypass72 that connects a downstream or outlet side of compressor 50 to anupstream or inlet side of compressor 50. Compressor bypass 72 includes acontrol valve 74 that is selectively opened to allow charge flow to bereturned to the inlet side of compressor 50 to reduce compressor surgeunder certain operating conditions, such as when an intake throttle 76is closed. Inlet supply conduit 26 may include a charge air cooler 36downstream from compressor 50 and intake throttle 76. In anotherembodiment, a charge air cooler 36 is located in the intake system 22upstream of intake throttle 76. Charge air cooler 36 may be disposedwithin inlet air supply conduit 26 between engine 30 and compressor 50,and embody, for example, an air-to-air heat exchanger, an air-to-liquidheat exchanger, or a combination of both to facilitate the transfer ofthermal energy to or from the flow directed to engine 30.

In operation of internal combustion engine system 20, fresh air issupplied through inlet air supply conduit 23. The fresh air flow orcombined flows can be filtered, unfiltered, and/or conditioned in anyknown manner, either before or after mixing with the EGR flow from EGRsystems 51, 60 when provided. The intake system 22 may includecomponents configured to facilitate or control introduction of thecharge flow to engine 30, and may include intake throttle 76, one ormore compressors 50, and charge air cooler 36. The intake throttle 76may be connected upstream or downstream of compressor 50 via a fluidpassage and configured to regulate a flow of atmospheric air and/orcombined air/EGR flow to engine 30. Compressor 50 may be a fixed orvariable geometry compressor configured to receive air or air and fuelmixture from fuel source 104 and compress the air or combined flow to apredetermined pressure level before engine 30. The charge flow ispressurized with compressor 50 and sent through charge air cooler 36 andsupplied to engine 30 through intake supply conduit 26 to engine intakemanifold 28.

With further reference to FIG. 2, fuel system 21 is configured toprovide dual fuelling of engine 30. Only four cylinders 31 a, 31 b, 31c, 31 d are shown in FIG. 2, it being understood that if additionalcylinders, such as cylinders 31 e and 31 f, or fewer cylinders, areprovided they are arranged in a manner similar to the illustratedcylinders 31. Fuel system 21 includes first fuel source 102 and secondfuel source 104. First fuel source 102 is configured to provide a flowof a first fuel to cylinders 31 with one or more injectors at or neareach cylinder. Second fuel source 104 is connected to intake system 22with a mixer or connection at or adjacent an inlet of compressor 50. Incertain embodiments, the cylinders 31 each include at least one directinjector for delivering fuel to the combustion chamber thereof from aprimary fuel source, such as first fuel source 102. In addition, atleast one of a port injector at each cylinder or a mixer at an inlet ofcompressor 50 can be provided for delivery or induction of fuel from thesecond fuel source 104 with the charge flow delivered to cylinders 31.

The fueling from the first fuel source 102 is controlled to provide thesole fueling at certain operating conditions of engine 30, and fuelingfrom the second fuel source 104 is provided to substitute for fuelingfrom the first fuel source 102 at other operating conditions to providea dual flow of fuel to engine 30. In embodiments where the first fuelsource 102 is diesel fuel and the second fuel source 104 is natural gas,a control system including controller 200 is configured to control theflow of liquid diesel fuel from first source 102 and the flow of gaseousfuel from second source 104 in accordance with the control parametersdisclosed herein.

A direct injector, as utilized herein, includes any fuel injectiondevice that injects fuel directly into the cylinder volume, and iscapable of delivering fuel into the cylinder volume when the intakevalve(s) and exhaust valve(s) are closed. The direct injector may bestructured to inject fuel at the top of the cylinder or laterally of thecylinder. In certain embodiments, the direct injector may be structuredto inject fuel into a combustion pre-chamber. Each cylinder 31 mayinclude one or more direct injectors 116 a-116 d, respectively. Thedirect injectors 116 a-116 d may be the primary fueling device for firstfuel source 102 for the cylinders 31.

A port injector, as utilized herein, includes any fuel injection devicethat injects the second fuel outside the engine cylinder in the intakemanifold to form the air-fuel mixture. The port injector injects thefuel towards the intake valve. During the intake stroke, the downwardsmoving piston draws in the air/fuel mixture past the open intake valveand into the combustion chamber. Each cylinder 31 a, 31 b, 31 c, 31 dmay include one or more port injectors 118 a, 118 b, 118 c, 118 d,respectively. In one embodiment, the port injectors 118 a-118 d may bethe primary fueling device for second fuel source 104 to the cylinders31. In another embodiment, the second fuel source 104 can be connectedto intake system 22 with a mixer 115 at a gaseous fuel connection 114upstream of intake manifold 28, such as at the inlet of or upstream ofcompressor 50. A flow control valve 117 can be provided to control theflow of gaseous fuel to engine 30 from second fuel source 104.

In certain embodiments, each cylinder 31 includes at least one directinjector that is capable of providing all of the designed fueling amountfrom first fuel source 102 for the cylinders 31 at any operatingcondition. Second fuel source 104 provides a flow of a second fuel toeach cylinder 31 through a port injector or a natural gas connectionupstream of intake manifold 28 to provide a second fuel flow to thecylinders 31 to achieve desired operational outcomes, such as improvedefficiency, improved fuel economy, improved high load operation, andother outcomes.

One embodiment of system 20 includes fuel system 21 with at least onefuel source 102 to provide a first fuel flow to all the cylinders 31 anda second fuel source 104 that provides a second fuel flow to all thecylinders 31 in addition to the first fuel flow under certain operatingconditions. First fuel source 102 includes a first fuel pump 105 that isconnected to controller 200, and the second fuel source 104 includes, inone embodiment, a second fuel pump 106 that is connected to controller200. Each of the cylinders 31 includes an injector, such as directinjectors 116 a-116 d associated with each of the illustrated cylinders31 a-31 d of FIG. 2. Direct injectors 116 a-116 d are electricallyconnected with controller 200 to receive fueling commands that provide afuel flow to the respective cylinder 31 in accordance with a fuelcommand determined according to engine operating conditions and operatordemand by reference to fueling maps, control algorithms, or otherfueling rate/amount determination source stored in controller 200. Firstfuel pump 105 is connected to each of the direct injectors 116 a-116 dwith a first fuel line 109. First fuel pump 105 is operable to provide afirst fuel flow from first fuel source 102 to each of the cylinders 31a-31 d in a rate, amount and timing determined by controller 200 thatachieves a desired power and exhaust output from cylinders 31.

If provided, second fuel pump 106 is connected to the inlet ofcompressor 50 with gaseous fuel connection 114 with a second fuel line108 or to port injectors 118. A shutoff valve 112 can be provided infuel line 108 and/or at one or more other locations in fuel system 21that is connected to controller 200. Second fuel pump 106 is operable toprovide a second fuel flow from second fuel source 104 in an amountdetermined by controller 200 that achieves a desired power and exhaustoutput from cylinders 31. In another embodiment, second fuel pump 106 isomitted and fuel is supplied to connection 114 or port injectors 118under pressure from a pressurized second fuel source 104, and the flowof gaseous fuel from second fuel source 104 is controlled by flowcontrol valve 117.

Controller 200 can be connected to actuators, switches, or other devicesassociated with fuel pumps 105, 106, shutoff valve 112, intake throttle76, compressor bypass valve 74, shutoff valve 112, flow control valve117, wastegate 70 and/or injectors 116, 118 and configured to providecontrol commands thereto that regulate the amount, timing and durationof the flows of the first and second fuels to cylinders 31, the chargeflow, and the exhaust flow to provide the desired power and exhaustoutput. The positioning of each of shutoff valve 112, flow control valve117, intake throttle 76, compressor bypass valve 74, wastegate 70,injectors 116, 118 and/or the on/off status of fuel pumps 105, 106 canbe controlled via control commands from controller 200.

In other embodiments, a first subset of cylinders 31 is associated witha first cylinder bank (not shown) and a second subset of cylinders 31 isassociated with a second cylinder bank. Accordingly, differingsubstitution rates of the gaseous fuel can be used for the cylinderbanks. In certain embodiments of engines with multiple cylinder banks,the feed lines for the gaseous fuel can be separately controlled to eachcylinder bank to provide the desired substitution rate of the gaseousfuel for the respective cylinder bank.

In certain embodiments of the systems disclosed herein, controller 200is structured to perform certain operations to control engine operationsand fueling of cylinders 31 with fueling system 21 to provide thedesired operational outcomes. In certain embodiments, the controller 200forms a portion of a processing subsystem including one or morecomputing devices having memory, processing, and communication hardware.The controller 200 may be a single device or a distributed device, andthe functions of the controller 200 may be performed by hardware orinstructions provided on a computer readable storage medium. Thecontroller 200 may be included within, partially included within, orcompletely separated from an engine controller (not shown). Thecontroller 200 is in communication with any sensor or actuatorthroughout the systems disclosed herein, including through directcommunication, communication over a datalink, and/or throughcommunication with other controllers or portions of the processingsubsystem that provide sensor and/or actuator information to thecontroller 200.

In certain embodiments, the controller includes one or more modulesstructured to functionally execute the operations of the controller. Thedescription herein including modules emphasizes the structuralindependence of the aspects of the controller, and illustrates onegrouping of operations and responsibilities of the controller. Othergroupings that execute similar overall operations are understood withinthe scope of the present application. Modules may be implemented inhardware and/or as computer instructions on a non-transient computerreadable storage medium, and modules may be distributed across varioushardware or computer based components. More specific descriptions ofcertain embodiments of controller operations are included in thesections referencing FIGS. 3, 5, 7, 9, 11, 12 and 13-16.

Example and non-limiting module implementation elements include sensorsproviding any value determined herein, sensors providing any value thatis a precursor to a value determined herein, datalink and/or networkhardware including communication chips, oscillating crystals,communication links, cables, twisted pair wiring, coaxial wiring,shielded wiring, transmitters, receivers, and/or transceivers, logiccircuits, hard-wired logic circuits, reconfigurable logic circuits in aparticular non-transient state configured according to the modulespecification, any actuator including at least an electrical, hydraulic,or pneumatic actuator, a solenoid, an op-amp, analog control elements(springs, filters, integrators, adders, dividers, gain elements), and/ordigital control elements.

One of skill in the art, having the benefit of the disclosures herein,will recognize that the controllers, control systems and control methodsdisclosed herein are structured to perform operations that improvevarious technologies and provide improvements in various technologicalfields. Without limitation, example and non-limiting technologyimprovements include improvements in combustion performance of dual fuelinternal combustion engines, improvements in engine torque generationand torque control, engine fuel economy performance, improvements inengine noise and vibration control for dual fuel engines, improvementsin performance or operation of aftertreatment systems and/or componentsof dual fuel engines, and/or improvements in emissions reduction in dualfuel engines. Without limitation, example and non-limiting technologicalfields that are improved include the technological fields of duel fuelinternal combustion engines and related apparatuses and systems as wellas vehicles including the same.

Certain operations described herein include operations to interpretand/or to determine one or more parameters. Interpreting or determining,as utilized herein, includes receiving values by any method known in theart, including at least receiving values from a datalink or networkcommunication, receiving an electronic signal (e.g. a voltage,frequency, current, or PWM signal) indicative of the value, receiving acomputer generated parameter indicative of the value, reading the valuefrom a memory location on a non-transient computer readable storagemedium, receiving the value as a run-time parameter by any means knownin the art, and/or by receiving a value by which the interpretedparameter can be calculated, and/or by referencing a default value thatis interpreted to be the parameter value.

The schematic flow descriptions which follow provide illustrativeembodiments of methods for controlling fuelling during a dual fuellingmode of operation of internal combustion engine system 20. As usedherein, a dual fuel system 21 is a fueling system in which a dualfueling mode is provided where each of the cylinders 31 of engine 30receives a first fuel flow and a second fuel flow in addition to thefirst fuel flow under certain operating conditions. However, it iscontemplated that the dual fueling system 21 can be operated in a singlefuel mode from first fuel source 102 upon operator selection or certainoperating conditions. Operations illustrated are understood to beexemplary only, and operations may be combined or divided, and added orremoved, as well as re-ordered in whole or part, unless statedexplicitly to the contrary herein. Certain operations illustrated may beimplemented by a computer or controller apparatus embodiment ofcontroller 200 executing a computer program product on a non-transientcomputer readable storage medium, where the computer program productcomprises instructions causing the computer to execute one or more ofthe operations, or to issue commands to other devices to execute one ormore of the operations.

FIG. 3 is a schematic illustration of one embodiment of a processingsubsystem 300 for controller 200 for controlling operations of dual fuelengine 30 in response to knock conditions. In certain applications, thesecond fuel has combustion characteristics that are highly variable.Processing subsystem 300 includes a knock definition module 302structured to determine an expected knock value 310 for a gaseous fuelfrom second fuel source 104 delivered to dual fuel engine 30, a knockdetermination module 304 structured to determine a current knock value312 for the gaseous fuel in the dual fuel engine 30, a knock adjustmentmodule 306 structured to determine an adjusted substitution rate 314 forthe gaseous fuel in response to comparing the expected knock value 310and the current knock value 312, and an engine control module 308structured to output a fuelling command 316 for fueling the dual fuelengine 30 in response to the adjusted substitution rate 314.

In one embodiment, subsystem 300 receives at least one of operatingparameters 318 associated with operation of dual fuel engine 30 and aknock sensor input 320 from a knock sensor associated with dual fuelengine 30. Operating parameters 318 can include any operating parameteror parameters suitable for indicating an expected knock value and/or acurrent knock value. Knock sensor input 320 can include any sensor orcombination of sensors suitable to provide an output of an expectedknock and/or current knock value associated with operation of the dualfuel engine 30.

In a further embodiment, subsystem 300 is configured to associate thecurrent knock value with an expected knock value that is predeterminedor determined outside of a time domain in which the operating parameters318 were used to determine the current knock value to account forvariations in quality of the gaseous fuel. In a refinement of thisembodiment, the one or more operating parameters 318 include an enginespeed, an engine load, a charge flow rate, an air flow rate, an intakemanifold temperature (IMT), an exhaust manifold temperature (EMT), anintake manifold pressure (IMP), an exhaust manifold pressure (EMP), anexhaust gas recirculation (EGR) temperature, oxygen amount, and anoxygen fraction. The knock value that occurs at the one or moreoperating parameters outside of the time domain in which the operatingparameters are determined can be used as the expected knock value thatis compared to the current knock value to determine the adjustedsubstitution rate for the second fuel.

Referring to FIG. 4, there is shown one embodiment of a procedure 400for operating dual fuel engine 30 with a liquid fuel from first fuelsource 102 and a gaseous fuel from second fuel source 104. In oneembodiment, the procedure 400 is implemented by processing subsystem300. Procedure 400 includes an operation 402 to determine an expectedknock value for the gaseous fuel in dual fuel engine 30. Procedure 400further includes an operation 404 to determine a current knock value forthe gaseous fuel in dual fuel engine. In one embodiment, the currentknock value is determined by fueling dual fuel engine 30 with an amountof the gaseous fuel that is greater than a requested amount of thegaseous fuel. The requested amount of the gaseous fuel can include oneor more of an amount of the gaseous fuel indicated by a nominalsubstitution rate of gaseous fuel for liquid fuel, and an amount of thegaseous fuel indicated by a substitution rate in use before the adjustedsubstitution rate.

Procedure 400 continues at operation 406 to determine an adjustedsubstitution rate for the gaseous fuel in response to comparing theexpected knock value and the current knock value. Operation 406 mayfurther include fuelling the dual fuel engine 30 with an amount of thegaseous fuel in response to the adjusted substitution rate. Procedure400 may further include an operation 408 to consider the operatingregion of the dual fuel engine, and to associate data regarding theexpected knock value, the current knock value, the nominal substitutionrate, the current substitution rate, and the adjusted substitution ratewith the operating region of the engine at the time the data isutilized. The operating region of the engine can be indicated by one ormore operating parameters, such as engine speed, engine load, chargeflow rate, air flow rate, IMT, EMT, IMP, EMP, EGR temperature, oxygenamount, and oxygen fraction.

In another embodiment, the current knock value is determined byobserving a knock event. A current substitution rate of the gaseous fuelfor the liquid fuel that is not expected to incur the knock event isthen determined for the adjusted substitution rate. The adjustedsubstitution rate can further be determined by observing a current knockevent and reducing a substitution rate until the knock event is nolonger observed so that the reduced substitution rate which does notcause the knock event can be determined and the adjusted substitutionrate can be determined from the determined reduced substitution rate.

In a further embodiment of procedure 400, operation 406 to determine theadjusted substitution rate for the gaseous fuel includes determining aneffective fuel substitution rate for the gaseous fuel. The effectivefuel substitution rate for the gaseous fuel includes a first amount ofgaseous fuel that provides an amount of effective torque equivalent to asecond amount of a liquid fuel. The effective fuel substitution rate isdistinct from a nominal fuel substitution rate.

FIG. 5 is a schematic illustration of another embodiment processingsubsystem 500 of controller 200 which is operable to determine theenergy content of the gaseous fuel by using the liquid fuel of knownenergy content to determine the energy demand of the dual fuel engineand controlling operations of duel fuel engine 30 in response.Processing subsystem 500 includes an engine output definition module 502structured to output a liquid fuel fraction increase operating command504 to operate dual fuel engine 30 at one of an increased liquid fuelfraction from first fuel source 102 and a 100% liquid fuel fraction fromfirst fuel source 102. Engine output definition module 502 is furtherstructured to determine an engine load value 506 while operating at theincreased liquid fuel fraction or 100% liquid fuel fraction. In oneembodiment, engine output definition module 502 is further structured tooperate dual fuel engine 30 at an increased liquid fuel fraction byreducing a gaseous fuel flow rate from a nominal gaseous fuel flow ratedetermined according to the nominal substitution rate. In a furtherembodiment, the gaseous fuel flow rate is reduced from the nominalgaseous fuel flow rate by one of a predetermined amount and a detectableamount.

Subsystem 500 also includes a fuel energy definition module 508structured to determine an expected fuel flow rate 510 in response to anominal substitution rate 512 of the gaseous fuel for the liquid fuel atthe engine load value 506 and a load substitution description 514. Theexpected fuel flow rate 510 includes one of a gaseous fuel rate and aresulting liquid fuel rate. The load substitution description 514includes a replacement amount of gaseous fuel 516 that provides anamount of torque equivalent to a replaced amount of a liquid fuel.

Subsystem 500 includes a fuel check module 518 structured to determineoperating conditions suitable for a partially substituted operatingcondition command 520 to operate the dual fuel engine 30 at a partiallysubstituted operating condition where a third amount of the liquid fuelis substituted with a fourth amount of the gaseous fuel. A fuel energyquality module 522 is structured to output a comparison 524 of an actualversus expected operating condition. In one embodiment, the comparisonis made between the resulting or actual liquid fuel rate 526 and theexpected fuel flow rate 510. In another embodiment, the comparison ismade between an effective gaseous fuel flow rate 528 and the replacementamount of the gaseous fuel 516 that was expected to occur. Subsystem 500further includes a fuel energy correction module 530 structured todetermine a nominal substitution rate adjustment 532 that adjusts thenominal substitution rate in response to the comparison 524.

Referring to FIG. 6A, there is shown another embodiment of a procedure600 for operating dual fuel engine 30 with a liquid fuel from first fuelsource 102 and a gaseous fuel from second fuel source 104. In oneembodiment, the procedure 600 is implemented by processing subsystem 500described above. Procedure 600 includes an operation 602 to operate dualfuel engine 30 on 100% liquid fuel from first fuel source 102 where afirst amount of liquid fuel is substituted for a second amount ofgaseous fuel, and an operation 604 to determine an engine load value inresponse to operation 602. Procedure 600 further includes an operation606 to determine an expected fuel flow rate in response to a nominalsubstitution rate of gaseous fuel for liquid fuel, a load substitutiondescription, and the engine load value. The expected fuel flow rateincludes one of a gaseous fuel rate and a resulting liquid fuel rate,and the load substitution description includes a replacement amount ofgaseous fuel that provides an amount of torque equivalent to a replacedamount of a liquid fuel.

Procedure 600 continues at an operation 608 to operate the dual fuelengine at a partially substituted operating condition where a thirdamount of the liquid fuel is substituted with a fourth amount of thegaseous fuel. At operation 610 a comparison of one of the resultingliquid fuel rate to the expected fuel flow rate is made, and atoperation 612 a comparison of an effective gaseous fuel flow rate to thereplacement amount of the gaseous fuel is made. Procedure 600 continuesat operation 614 to adjust the nominal substitution rate in response tothe comparisons from at least one of operations 610 and 612. In oneembodiment, operation 614 includes adjusting one of the nominalsubstitution rate and the load substitution description in response tothe effective gaseous flow rate and the replacement amount of thegaseous fuel. In another embodiment, operation 614 includes adjustingone of the nominal substitution rate and the load substitutiondescription in response to the expected fuel flow rate and the thirdamount of the liquid fuel.

In another embodiment of procedure 600, operation 602 includes operatingdual fuel engine 30 on a first gaseous fuel amount that is less than thegaseous fuel amount indicated by a nominal substitution rate by apredetermined amount and on a second liquid fuel amount. Operation 606includes determining an expected fuel flow rate in response to a nominalsubstitution rate, a load substitution description and the predeterminedamount. This embodiment further includes operating the dual fuel engineat a partially substituted operating condition where a third amount ofthe liquid fuel is substituted with a fourth amount of the gaseous fuel,and the partially substituted operating condition includes a greateramount of the gaseous fuel than the first gaseous fuel amount.

Referring now to FIG. 6B, another embodiment procedure 650 includes anoperation 652 to induce a change in the dual fuel engine 30 to operateat a prescriptively reduced or eliminated gas fuel fraction. In oneembodiment, the procedure 650 is implemented by processing subsystem500. Procedure 650 includes an operation 654 to determine a torque makeup amount of liquid fuel utilized to maintain at least one of an enginespeed, an engine load, and an engine power after completion of operation652. Procedure 650 continues at operation 656 to determine an effectivegas flow rate in response to the torque make up amount of liquid fueland the prescriptively reduced or eliminated gas fuel fraction, and anoperation 658 to adjust at least one of a nominal substitution rate ofthe gaseous fuel and a load substitution description in response to theeffective gas flow rate.

FIG. 7 is a schematic illustration of another embodiment processingsubsystem 700 of controller 200 for controlling the gaseous fuellingrate by determining the heat energy of the gaseous fuel and controllingoperations of duel fuel engine 30 in response. Processing subsystem 700includes an energy dissipation module structured 702 to determine afirst work amount 704 for an operating duel fuel engine 30 and a firstheat dissipation amount 706 for the operating dual fuel engine 30.Subsystem 700 includes an energy generation module 708 structured todetermine a fuel energy amount 710 for the operating dual fuel engine 30in response to a liquid fuel amount 712 and a gaseous fuel amount 714.

Subsystem 700 further includes a fuel quality determination module 716structured to determine a gaseous fuel quality value 718 and/or aparameter representative thereof in response to the fuel energy amount710, the first heat dissipation amount 706, the first work amount 704,the liquid fuel amount 712, and the gaseous fuel amount 714. Inembodiment, the heat energy of the engine is determined from the exhausttemperature and mass flow of the exhaust, and the heat energy and brakespecific horsepower of the engine are used to determine the fuel energyamount of the first and second fuel amounts 712, 714. The contributionof the liquid fuel to the fuel energy is constant, so variations in thefuel energy amount are attributed to the quality of the gaseous fuel. Afuel energy correction module 720 is structured to adjust at least oneof a nominal substitution rate 722 and a load substitution description724 of the gaseous fuel in response to the gaseous fuel quality value718.

In one embodiment, dual fuel engine includes a sensor 82 (FIG. 1) thatis configured to provide an output signal indicative of a heat transferenvironment of engine 30, and subsystem 700 is configured to determineif engine 30 is operating in a nominal heat transfer environment. In afurther embodiment, turbocharger 46 has a turbine side including turbine48 disposed in an exhaust gas stream of engine 30, and the energydissipation module 702 is structured to define a downstream boundary forenergy balance 726 for system 100 at an upstream side of the turbine 48.In another embodiment, energy dissipation module 702 is structured todefine the downstream boundary for system energy balance 726 at adownstream side of the turbine 48.

Referring to FIG. 8, there is shown another embodiment of a procedure800 for operating dual fuel engine 30 with a liquid fuel from first fuelsource 102 and a gaseous fuel from second fuel source 104. In oneembodiment, the procedure 800 is implemented by processing subsystem700. Procedure 800 includes an operation 802 to determine a first workamount for an operating dual fuel engine 30. Procedure 800 furtherincludes an operation 804 to determine a first heat dissipation amountfor the operating dual fuel engine 30. In one embodiment, the heatdissipation amount is determined by a determination that an excessthermal energy amount is present in an exhaust gas of the engine.

Procedure 800 includes an operation 806 to determine a fuel energyamount for the operating dual fuel engine 30 in response to a liquidfuel amount and a gaseous fuel amount. In one embodiment, the fuelenergy amount is determined in response to determining the dual fuelengine 30 is operating in a nominal heat transfer environment. In afurther embodiment, determining the fuel energy amount includesperforming a system energy balance, and defining a downstream boundaryof the system at one of upstream of a turbine and downstream of aturbine.

Procedure 800 continues at an operation 808 to determine a gaseous fuelquality value or parameter representative thereof in response to thefuel energy amount, the first heat dissipation amount, the first workamount, the liquid fuel amount, and the gaseous fuel amount. Procedure800 continues at operation 810 to adjust at least one of a nominalsubstitution rate and a load substitution description in response to thegaseous fuel quality value. Operation 810 can further include operationsto adjust the at least one of the nominal substitution rate and the loadsubstitution description to compensate for an engine knock effect,operations to adjust the at least one of the nominal substitution rateand the load substitution description to compensate for a fuel injectortip temperature effect, and operations to adjust the at least one of thenominal substitution rate and the load substitution description tocompensate for an exhaust gas temperature effect.

In a further embodiment of procedure 800, the duel fuel engine isdetermined to be operating in a nominal heat transfer environment inresponse to at least one of determining that an engine coolanttemperature is within a predetermined range (inclusive), determiningthat an ambient air temperature is within a predetermined range(inclusive), and determining that a vehicle speed is within apredetermined range (inclusive).

FIG. 9 is a schematic illustration of another embodiment processingsubsystem 900 of controller 200 that adjusts engine operating parametersof duel fuel engine 30 in response to gaseous fuel quality. Processingsubsystem 900 includes a gas composition definition module 902structured to receiver an input of gaseous fuel parameters 904 and todetermine a gas composition parameter 906 for the gaseous fuel providedto dual fuel engine 30. The gas composition parameter 906 includes atleast one parameter that is a fuel energy content description and/or aknock tendency description. Subsystem 900 further includes a combustionmanagement module 908 structured to provide an adjusted base fuelingrecipe 910 in response to the gas composition parameter 906 to reduce,eliminate or avoid operating conditions in which knock, reduced enginepower output, or other situations are likely to occur.

The adjusted base fueling recipe 910 includes one or more parametersadjusted for gaseous fuel quality, including a gaseous fuel substitutionrate, an air-fuel-ratio, a liquid fuel injection timing, a liquid fuelinjection pressure, a valve timing selection, an oxygen fraction value,an oxygen amount value, an EGR flow rate value, an EGR fraction value,an IMT value, an IMP value, a charge flow value, and a chargetemperature value. Subsystem 900 further includes an engine controlmodule 912 structured to output a fuelling command 914 that provides afirst amount of the gaseous fuel from second fuel source 104 and asecond amount of a liquid fuel from first fuel source 102 to theinternal combustion engine in response to the adjusted base fuelingrecipe 910.

Referring to FIG. 10, there is shown another embodiment of a procedure1000 for operating dual fuel engine 30 with a liquid fuel from firstfuel source 102 and a gaseous fuel from second fuel source 104. In oneembodiment, the procedure 1000 is implemented by processing subsystem900. Procedure 1000 includes an operation 1002 to determine a gascomposition parameter for the gaseous fuel provided to dual fuel engine30. The gas composition parameter includes at least one of a fuel energycontent description and a knock tendency description. In one embodiment,the fuel energy content description indicates a fuel energy content ofthe gaseous fuel that is higher or lower than a nominal fuel energyvalue of the gaseous fuel. In a further embodiment, the knock tendencydescription indicates a methane number that is higher or lower than anominal methane number for the gaseous fuel.

Procedure 1000 continues at operation 1004 to adjust the base fuellingrecipe in response to the gas composition parameter. Operation 1004 caninclude an operation 1006 that adjusts the base fuelling recipe byadjusting a liquid fuel injection timing and/or pressure in response toa knock tendency indicator indicating a methane number higher or lowerthan a nominal methane number for the gaseous fuel. Operation 1004 canalso include an operation 1008 that adjusts the base fuelling recipe byadjusting by increasing or decreasing of the amount of the gaseous fuelprovided to the engine in response to the fuel energy content beinglower or higher, respectively, than the nominal fuel energy value of thegaseous fuel. Operation 1004 can include an operation 1010 that adjuststhe base fuelling recipe by adjusting a load substitution description,an operation 1012 that adjusts the base fuelling recipe by adjusting anominal substitution rate of the gaseous fuel for the liquid fuel,and/or an operation 1014 that adjusts the base fuelling recipe byadjusting at least one of a target EGR rate and a target charge flowvalue in response to the fuel energy content being higher of lower thanthe nominal fuel energy content, and/or in response to the methanenumber being higher or lower than the nominal methane number. Procedure1000 continues at operation 1016 to provide a first amount of thegaseous fuel from second fuel source 104 and a second amount of theliquid fuel from first source 102 to dual fuel engine 30 in response tothe adjusted base fueling recipe.

FIG. 11 is a schematic illustration of another embodiment processingsubsystem 1100 of controller 200 for evaluating a quality of the gaseousfuel and adjust operations of dual fuel engine 30 in response to thesame. Processing subsystem 1100 includes a performance check module 1102structured to output a fuelling command 1104 the fuelling system 21 toprovide only liquid fuel from first fuel source 102 to a first one ofthe combustion chambers of cylinder 31, and to provide both gaseous fueland liquid fuel to the remaining combustion chambers of cylinders 31.Subsystem 1100 further includes a performance differentiation module1106 structured to interpret a combustion performance indicator 1108associated with the first combustion chamber and its differentiationwith the combustion performance in the remaining cylinders 31, and tointerpret an aggregate performance indicator 1110. The aggregateperformance indicator 1110 includes at least one of a bulk exhaust gastemperature, an average combustion event torque contribution, a modeledcombustion event parameter, and a predetermined combustion eventparameter stored in a non-transient memory location.

Subsystem 1100 further includes a gaseous fuel definition module 1112structured to determine a gas composition parameter 1114 in response tothe combustion performance indicator 1108 and the aggregate performanceindicator 1110. A composition response module 1116 is structured to, inresponse to the gas composition parameter 1114, to output one orcommands to perform at least one operation that includes adjusting abase fuelling recipe 1118, to adjust a nominal substitution rate 1120,to adjust a load substitution description 1122, and/or to store the gascomposition parameter 1124 such as in a non-transient memory location ofcontroller 200. In one embodiment, the load substitution description isa replacement amount of the gaseous fuel that provides an amount oftorque equivalent to the replaced amount of the liquid fuel.

In one embodiment, the composition response module 1116 is furtherstructured to adjust the base fueling recipe by outputting a commandthat adjusts at least one of a target EGR rate and a target charge flowvalue, a liquid fuel injection timing of liquid fuel from first fuelsource 102, and/or a liquid fuel injection pressure. In anotherembodiment, the composition response module 1116 to determine the gascomposition parameter 1114 indicates at least one of an increased knocktendency and a reduced methane number of the gaseous fuel. In responseto this determination, the composition response module 1116 outputs acommand to perform at least one of retarding a liquid fuel injectiontiming, reducing a liquid fuel injection pressure, increasing a gaseousphase air-fuel-ratio by increasing a fresh air flow rate to the intakesystem, and increasing a gaseous phase air-fuel-ratio by decreasing anamount of the gaseous fuel.

In one embodiment, the combustion performance indicator 1108 is outputby a performance isolation device 84 (FIG. 2) that is associated withcombustion chamber 33 a of cylinder 31 a and structured to determine thecombustion performance indicator. The combustion performance indicatorof cylinder 31 a is at least partially isolated from the combustionperformance of the remaining ones of the plurality of the combustionchambers of cylinders 31. The performance isolation device 84 can be atemperature sensor positioned to determine an exhaust gas temperature ofthe combustion chamber 33 a. In another embodiment, performanceisolation device 84 is a temperature sensor positioned to determine anexhaust gas temperature of the plurality of combustion chambers forcylinders 31, where the temperature of the exhaust gas from combustionchamber 33 a is preferentially weighted. In yet another embodiment, theperformance isolation device is a temperature sensor positioned todetermine an in-cylinder temperature of the combustion chamber 33 a ofcylinder 31 a. In yet another embodiment, performance isolation device84 is an accelerometer structured to determine a torque contribution ofthe combustion chamber 33 a. In still another embodiment, performanceisolation device 84 is a pressure sensor positioned to determine anin-cylinder pressure of combustion chamber 33 a.

FIG. 12 is a schematic illustration of another embodiment processingsubsystem 1200 of controller 200. Processing subsystem 1200 includes anengine condition module 1202 structured to receive operating parameters1204 associated with operation of dual fuel engine 30 and interpret anengine operating value 1206. Subsystem 1200 further includes a fuelcontrol module 1208 structured to provide, in response to the engineoperating value 1206, at least one first fuel source command 1210 tofirst fuel source 102 and at least one second fuel source command 1212to second fuel source 104 such that a first ratio of the diesel liquidfuel to the gaseous fuel (d1:g1) in a first one of the cylinders 31 isdistinct from a second ratio of the diesel fuel to the gaseous fuel(d2:g2) in the a second one or more of the cylinders 31.

In one embodiment, the engine operating value 1206 is a fuel injectortip temperature value of injector 116 a. Fuel control module 1208 isstructured to increase the ratio d1:g1 to reduce the fuel injector tiptemperature value for the injector tip of injector 116 a in the firstcylinder 31 a. In a further embodiment, fuel control module 1208 isfurther structured to alternate increased diesel fuel ratios betweencylinders 31, to reduce the fuel injector tip temperature valuescorresponding to the injector tips of the injector 116 of each of thecylinders 31.

In another embodiment, the second fuel system associated with secondfuel source 104 includes one of gaseous port injection and gaseousdirect injection for delivery of gaseous fuel. The engine operatingvalue 1206 is a gaseous injector failure value defined by one or more ofprotection limits 1218 and failure limits 1220 corresponding to a firstone of the cylinders 31, and the fuel control module 1208 is structuredto modify the ratio d1:g1 in response to the gaseous injector failurevalue. Fuel control module 1208 can further be structured to increase adiesel fueling amount to the first one of the cylinders 31 in responseto the gaseous injector failure value indicating a gaseous fuel injectoroperationally coupled to the respective cylinder 31 is delivering lessthan a scheduled fueling amount of gaseous fuel. Fuel control module1208 can also be structured to increase a gaseous fueling amount in theremaining cylinders 31 in which a gaseous fuel injector failure is notindicated to maintain an overall substitution rate of gaseous fuel forliquid fuel. Fuel control module 1208 further be structured to decreasea diesel fueling amount to the respective cylinder 31 in response to thegaseous injector failure value indicating a gaseous fuel injectoroperationally coupled to the cylinder 31 is delivering greater than ascheduled fueling amount of gaseous fuel.

In another embodiment, the fuel control module 1208 is structured toprovide the first fuel source command to first fuel source 102 such thatone of the cylinders 31 is fully fueled with diesel in response to anengine operating value 1206 that is an emissions value. The emissionsvalue can include one or more of an aftertreatment componentregeneration request, an unburned hydrocarbons value, and an exhausttemperature value.

In another embodiment, subsystem 1200 includes a transient detectionmodule 1214 structured to provide the engine operating value 1206 as atransient duty cycle value 1216. The transient detection module 1214 isfurther structured to provide the engine operating value 1206 by one ormore of utilizing a high pass filtered load value of the engine 30,utilizing a derivative load value of the engine 30, utilizing a slopevalue of moving average engine load values 30, accepting an operatorinput indicating an upcoming transient, and interpreting a load schedule(e.g. a pump schedule) indicating an upcoming transient.

In one embodiment, where the dual fuel engine is employed in, forexample, drilling applications, the transient detection module 1214 isconfigured to interpret a geological formation from a reference table,chart or other input, and locations in the geological formation thatwill or are predicted to induce transients spikes in engine output areidentified. The substitution rate of gaseous fuel for liquid fuel can beproactively decreased in one or more of the cylinders 31 to providegreater liquid fuelling and improve the capability of the engine toresponse to the transient spikes. In another embodiment, dual fuelengine 30 includes multiple cylinder banks and one of the cylinder banksis fuelled at a lower substitution ratio to increase the liquid fuelamount in response to the detected or anticipated transient conditionspike. In still another embodiment, a portion of the cylinders 31 areoperated in a liquid fuel only mode and the remaining cylinders 31 areoperated in a duel fuel mode. In yet another embodiment, a portion ofthe cylinders 31 are operated with a first substitution rate that isless than a substitution rate in the remaining cylinders.

With reference to FIG. 13 there is illustrated a flow diagram of anexemplary controls process 1300 for dual fuel substitution rateoptimization in the presence of engine knock. Process 1300 begins atoperation 1302 in which a target gaseous fuel substitution value isdetermined based upon engine load information, intake manifoldtemperature information, and gaseous fuel quality information. In apreferred embodiment, the determination is made using a set ofthree-dimensional tables which specify a plurality of discretesubstitution rate values as a function of the engine load information,the intake manifold temperature information, and the gaseous fuelquality information. The set of tables may include two or more tables.Interpolation may be performed to provide substitution ratedeterminations between discrete table values. The gaseous fuelsubstitution values in the tables may be determined empirically such asby testing in a test cell and/or by analysis or modeling. The tablevalues preferably consider the knock margin of the engine, as well asother parameters such as gas and component temperatures. The tablesgenerally specify higher substitution rates for higher gaseous fuelquality values, lower intake manifold temperature values, lower engineloads values, and higher engine RPMs. The tables also preferably reducethe substitution rate at very low loads, where the engine does not runas well in dual fuel mode.

The engine load information may be expressed in a variety of units orterms including, for example, as a percentage of a rated engine load ormaximum engine load or in terms of engine output power or output torque.The engine load information may be determined using one or more physicalsensors, virtual sensors, engine models accounting for energy producedby combustion and losses associated with the engine, or combinationsthereof. The intake manifold temperature information may be expressed ina number of units or terms including, for example, temperature values orpercentages or indices relating thereto. The intake manifold temperatureinformation may be determined using a one or more physical sensors,virtual sensors, models ambient temperature and added heat from intakecharge compression or other heat sources, or combinations thereof. Thegaseous fuel quality information may be expressed in a variety of unitsor terms including, for example, as a methane number, as a percentage ofa rated or maximum energy content or as an energy content value. Thegaseous fuel quality information may be determined based uponinformation provided by an operator, or may be determined using thetechniques disclosed herein without a priori knowledge of the gaseousfuel quality and without external input into the system such as operatorinput.

In certain embodiments the engine load information is expressed as apercent engine load, the intake manifold temperature is expressed as atemperature value, and the gaseous fuel quality information is expressedas a methane number (MN). While these parameters may be utilized in thedescription herein, they are understood to be non-limiting examples. Itshall be further understood that any parameters described herein may betransformed, approximated, estimated, or otherwise augmented or modifiedduring various controller operations.

From operation 1302, process 1300 proceeds to conditional 1304 whichdetermines whether the operator has provided gaseous fuel qualityinformation or set a gaseous fuel quality value and/or parameterrepresentative thereof. If conditional 1304 determines that the operatorhas provided gaseous fuel quality information or set a gaseous fuelquality value, process 1300 proceeds to operation 1306 which utilizesthe operator provided or set gaseous fuel quality value. If conditional1304 determines that the operator has not provided gaseous fuel qualityinformation or set a gaseous fuel quality value, process 1300 proceedsto operation 1308 which sets a conservatively low initial value forgaseous fuel quality a starting point for optimization, for example, amethane number of 50 may be used.

From either operation 1306 or operation 1308, process 1300 proceeds toconditional 1310 which determines whether engine knock is detected. Ifconditional 1310 does not determine that engine knock is present,process 1300 proceeds to operation 1312 which increases the gaseous fuelquality value based on a programmable or calibratible rate, for example,increasing methane number by one every 10 seconds. If conditional 1310detects engine knock, process 1300 proceeds to operation 1314 whichreduces the gaseous fuel substitution value sharply (for example by20-50% or more) to protect the engine and decreases the gaseous fuelquality value by a programmable or calibratible amount, for example,decreasing methane number by one. After a programmable delay or someother trigger, the algorithm increases the substitution rate again andtargets the substitution rate indicated by the gaseous fuel qualityvalue (for example one less than before).

From operations 1312 and 1314, process 1300 proceeds to conditional 1316which evaluates whether a knock limit has been reached, for example,whether knock has been encountered a certain number of times. Ifconditional 1316 determines that a knock limit has been reached, process1300 proceeds to operation 1318 which stops incrementing the gaseousfuel quality value if knock has been encountered a certain programmablenumber of times or, alternatively waits for a programmable amount oftime or another event such as a key off, or gaseous fuel switching offbefore returning to conditional 1310 and allowing the gaseous fuelquality values to be incremented again.

Certain embodiments are configured to account for the possibility thatat low engine loads the characteristics of diesel combustion mayincorrectly trigger knock detection. To avoid reducing the substitutionrate when it is not needed, an ignore zone conditional may be providedin process 1310, for example, immediately prior to conditional 1310 orconditional 1316. The ignore zone conditional evaluates whether theengine is operating in a region where it is known that the knock marginis more than sufficient, allowing the possibility of knock to be ruledout. The ignore zone may be a function of engine RPM, engine load andintake manifold temperature (e.g., low RPM and/or low intake manifoldtemperature). If apparent knock is detected in the ignore zone, thealgorithm ignores the knock signal. At the edge of the ignore zone, thealgorithm lowers its sensitivity to the knock signal (i.e. requires astronger knock signal before it takes action).

With reference to FIG. 14 there is illustrated a block diagram ofexemplary controls 1400. Controls 1400 include three dimensionalsubstitution rate reference tables 1416 which are structured to use anintake manifold temperature value 1403, a percent engine load value1404, and a methane number (MN) value which is output by a knockincrement/decrement counter block 1414 as inputs to determine and outputa target substitution rate. Block 1414 determines a MN parameter basedupon input from a low level knock threshold block 1412 which, in turndetermines and provides to block 1414 an up or down value based uponinput from knock intensity block 1401. A further example of MNdetermination controls is described in connection with FIG. 15 below.

Blocks 1402, 1415, and 1418 are structured to monitor the diesel fuelrate (or other liquid fuel rate). If the diesel fuel flow rate goesbelow a calibrated value, the closed-loop substitution rate PIDreference is switched from the values determined from the threedimensional tables 1416 to a minimum diesel fueling setpoint. This iseffective to maintain a minimum level of diesel fueling to ensure goodgas combustion.

Block 1419 is structured to determine an error between a targetsubstitution rate provided from block 1418 and an actual substitutionrate 1405. This error is provided as an input to block 1420. Blocks1420, 1422, 1424, 1406, 1416, 1430 and 1440 are structured to determinea gaseous fuel valve opening or position control parameter which isutilized to control gaseous fuel control valve 1490. More specificallyblock 1420 sets minimum and maximum authority table limits based uponinput power. Block 1422 determines a valve control command based on aramp rate and a PID output from block 1420 which, implements a gassubstitution PID loop based upon the input substitution rate error.Block 1406 provides an open loop alternate input to set a valve controlcommand. Block 1430 provides a feed forward knock pull back alternateinput. It shall be appreciated that if the diesel fueling value ishigher than the minimum value, the targeted PID reference comes from thethree dimensional tables using percent engine load, intake manifoldtemperature and MN parameters. Within the limits of authority, theclosed loop controls maintain the gas substitution rate to thepercentage prescribed by the three dimensional tables.

It shall be appreciated that the controls 1400 utilize three-dimensionaltables to vary the knock detection threshold as a function of engineload and intake manifold temperature. Since actual gas knock levels aredetermined primarily by engine load, gas methane number and intakemanifold temperature a variable threshold can be used to ignore regionsof engine operation where gas knock will not occur. This variable knockdetection threshold also allows a consistent knock margin over the rangeof engine load and intake manifold temperature. It shall be furtherappreciated that controls 1400 provide control of gas fuel substitutionvalues in the presence of diesel combustion noise.

With reference to FIG. 15 there is illustrated a block diagram ofcontrols 1500 which are structured to determine knock intensity and agaseous fuel substitution rate value. Controls 1500 includes gaseousfuel substitution rate block 1550 which is structured to determine andoutput a gaseous fuel substitution rate value 1554 based upon a percentengine load input value 1551, an intake manifold temperature value 1552and a gaseous fuel quality input value 1553 which is expressed in termsof methane number (MN) in the illustrated embodiment. In a preferredform block 1550 is structured to utilize a set of three dimensional gassubstitution rate reference tables to determine the output value basedupon the input values 1551, 1552, and 1553. This allows tailoring of theknock detection level to ignore regions of engine operation where knockwill not occur. A knock feed-forward term and knock shutdown logic forheavy knock may also be utilized.

Gaseous fuel quality block rate block 1541 outputs gaseous fuel qualityinput value 1553 to gaseous fuel substitution rate block 1550. Anoperator input 1545 or separate controller input 1543 may selectably setblock 1541 to utilizes a gaseous fuel quality value and/or parameterrepresentative thereof external to the system, such as a value providedby the operator or controller or, alternatively, to utilize a gaseousfuel quality value and/or parameter representative thereof determined byblock 1520. Block 1520, in turn, receives inputs from module 1510. Morespecifically, percent detonation information is provided to knock detectblock 1521. In addition, a knock level value corresponding to asufficiently severe knock amount such that gas is completely turned offand the engine returns to diesel only mode is provided to logical “AND”block 1540. Knock detect module 1521 interprets the detonationinformation relative to a threshold value and provides output to logical“AND” block 1540, logical “NOT” block 1522, and counters 1523, 1525, and1527 which track the number of knock events and the time between knockevents. For every knock event output by block 1521, the Max Knock Countof counter 1523 is increased and the MN Up/Down counter 1530 isdecreased by one count. The output of the Up/Down counter 1530 ismultiplied by the MN Authority scalar 1532 and the output is checked fora minimum and maximum value by the Min/Max Limit logic 1534.

The output MN parameter is provided to block 1540 and may be used toadjust the substitution rate reference table output. If the MN parameterincreases, the substitution rate reference will increase and more gaswill flow. If the MN parameter decreases, less gas will flow and theprobability of knock will decrease. If knock continues, the Up/Downcounter will continue to decease to lower the substitution rate to alevel that eliminates gas knock. If more than “n” knock events occur (acalibration value, in this case set to 2) the Up/Down counter isinhibited so that the engine does not repeatedly try to raise thesubstitution rate level to a level where knock occurs. This eliminatesthe continuous cycling of the gas substitution rate that existed in theprevious controls. Other criteria could be used to determine if thealgorithm should attempt to look for a more accurate MN parameter; i.e.a fixed time delay, ECM Key Off or significant changes in operatingcondition or switching gas on or off. If the engine is in a constantknock condition and the knock signal is continuously at a logic 1 level,the programmable 10 second clock allows the Up/Down counter to continueto decrease the MN variable every 10 seconds and thus decrease thesubstitution rate to eliminate knock. Assuming that the maximum KnockCount value “n” has not been reached, the Up/Down counter value willincrease by one count for every 20 second period (a programmablesetpoint) where there is no knock detected. This allows the MN parameterto increase and increase the gas substitution rate, thus optimizing thegas substitution level if no knock occurs. The substitution rate willincrease to a value equal to the maximum value allowed for the currentengine load and intake manifold temperature.

It shall be appreciated that in the disclosed knock controls, the dualfuel engine gas substitution rate can be controlled to the highestsubstitution rate possible for the engine operating conditions withoutany manual intervention. This automatic knock control strategy accountsfor changes in ambient temperature, engine conditions, cooling systemefficiency or gas quality without the operator needing to manuallychange the dual fuel control settings.

With reference to FIG. 16 there is illustrated a block diagram ofexemplary knock controls 1600 which are structured to protect adual-fuel internal combustion engine system from certain knock events.Controls 1600 are structured to protect against heavy knock but penalizethe gas substitution rate when such knock occurs. Controls 1600 includea knock sensing module 1610 which is structured to interpret informationfrom a plurality of knock sensors. The knock sensors may be physicalsensors, virtual sensors or combinations thereof. The knock sensors maycorrespond to the number of cylinders of a given engine. Knock sensingmodule 1610 provides knock level information to comparator 1625,immediate shutdown force block 1630, and gas reduction block 1640 of gascontrol module 1620. When the knock level information is above firstthreshold level, comparator 1625 illuminates a knock indicator such as aknock lamp. When the knock level information is above a second thresholdlevel, which may be the same as or different from the first thresholdlevel, immediate shutdown force block 1630 forces a gas fuel controlvalve position closed to a predetermined position to reduce gas flow andilluminates knock lamp 1660. Concurrently, the gas substitution ratereference level is reduced by gas reduction block 1640 which provides areduction value to block 1650 which subtracts the reduction value fromthe fuel control valve input and provides an adjusted fuel control valvecommand 1670.

Controls 1600 protect the engine from knock damage. More specifically,when the feed-forward gas pullback occurs the current control algorithmwaits a predetermined time before gradually attempting an increase insubstitution rate. Graph 1700 in FIG. 17 illustrates a sequence of knockcontrol events during a startup with 50 methane number (MN) gaseous fuelat an engine power level 1730 (indicated by the line marked withtriangles.) The block-shaped trace 1720 shows the substitution rateincreasing at a constant rate upon startup. As the substitution rateincreases, so does the detonation level 1705 as shown at the bottom ofthe graph 1700. When the detonation level 1705 exceeds a threshold, theknock feed-forward signal 1710 (indicated by the line with “x” markedtherealong) is asserted and the gas valve position 1740 (indicated bythe line with dots marked therealong) is immediately reduced to lowerthe gas flow. This reduction of substitution rate continues for aprogrammable time period. After this delay, the current knock controlalgorithm starts to increase the gas substitution rate (in FIG. 7 thisoccurs at ˜10 min). As shown, this gas rate increases to improvesubstitution rate but results in another knock event at ˜11 min. At thispoint the controls shut off gas flow due to knock to prevent acontinuous oscillation between the lower pullback substitution rate andthe substitution rate that caused the knock pull back.

As is evident from the figures and text presented above, a variety ofaspects according to the present disclosure are contemplated. Accordingto one aspect, a method includes determining an expected knock value fora gaseous fuel in a dual fuel engine; determining a current knock valuefor the gaseous fuel in a dual fuel engine; determining an adjustedsubstitution rate for the gaseous fuel in response to comparing theexpected knock value and the current knock value; and fueling the dualfuel engine with an amount of the gaseous fuel in response to theadjusted substitution rate.

In one embodiment of the method, determining the current knock valueincludes fueling the dual fuel engine with an amount of the gaseous fuelthat is greater than a requested amount of the gaseous fuel. In arefinement of this embodiment, the requested amount of the gaseous fuelincludes at least one of an amount of the gaseous fuel indicated by anominal substitution rate and an amount of the gaseous fuel indicated bya substitution rate in use before the adjusted substitution rate.

In another embodiment, determining the current knock value includesobserving a knock event, and determining that a current substitutionrate is not expected to incur the knock event. In a refinement of thisembodiment, determining the current knock value further includesreducing a substitution rate until the knock event is no longerobserved, and determining the reduced substitution rate which does notcause the knock event.

In another embodiment, the method includes considering the operatingregion of the engine, and associating data regarding expected knockvalue, current knock value, nominal substitution rate, currentsubstitution rate, and adjusted substitution rate with the operatingregion of the engine at the time the data is utilized. In a refinementof this embodiment, the operating region of the engine includes at leastone parameter selected from the parameters consisting of: engine speed,engine load, charge flow rate, air flow rate, IMT, EMT, IMP, EMP, EGRtemperature, oxygen amount, and oxygen fraction.

In another embodiment of the method, determining the adjustedsubstitution rate for the gaseous fuel includes determining an effectivefuel substitution rate for the gaseous fuel, the effective fuelsubstitution rate for the gaseous fuel including a first amount ofgaseous fuel that provides an amount of effective torque equivalent to asecond amount of a liquid fuel. In a refinement of this embodiment, theeffective fuel substitution rate is distinct from a nominal fuelsubstitution rate.

According to another aspect, a system includes a duel fuel engine and acontroller. The controller includes a knock definition module structuredto determine an expected knock value for a gaseous fuel in the dual fuelengine, a knock determination module structured to determine a currentknock value for the gaseous fuel in the dual fuel engine, a knockadjustment module structured to determine an adjusted substitution ratefor the gaseous fuel in response to comparing the expected knock valueand the current knock value, and an engine control module structured tocommand fueling for the dual fuel engine in response to the adjustedsubstitution rate.

In one embodiment of the system, the dual fuel engine includes a firstgaseous fuel source providing the gaseous fuel and a second liquid fuelsource providing a liquid fuel. In a refinement of this embodiment, thesystem includes a means for determining the expected knock value and/ora means for determining the current knock value. In still anotherembodiment of refinement of the previous embodiment, the system includesa means for associating the current knock value and the expected knockvalue outside of the time domain. In a refinement of this embodiment,the means for associating the current knock value and the expected knockvalue outside of the time domain further includes a means forassociating the current knock value and the expected knock value by atleast one parameter selected from the parameters consisting of: enginespeed, engine load, charge flow rate, air flow rate, IMT, EMT, IMP, EMP,EGR temperature, oxygen amount, and oxygen fraction.

According to another aspect, a method includes operating a dual fuelengine on 100% liquid fuel, and determining an engine load value;determining an expected fuel flow rate in response to a nominalsubstitution rate, a load substitution description, and the engine loadvalue, where the expected fuel flow rate includes one of a gaseous fuelrate and a resulting liquid fuel rate, and where the load substitutiondescription includes a replacement amount of gaseous fuel that providesan amount of torque equivalent to a replaced amount of a liquid fuel;operating the dual fuel engine at a partially substituted operatingcondition where a third amount of the liquid fuel is substituted with afourth amount of the gaseous fuel; comparing one of: the resultingliquid fuel rate to the expected fuel flow rate and an effective gaseousfuel flow rate to the replacement amount of the gaseous fuel, andadjusting the nominal substitution rate in response to the comparing.

According to one embodiment of the method, adjusting includes adjustingone of the nominal substitution rate and the load substitutiondescription in response to the effective gaseous flow rate and thereplacement amount of the gaseous fuel. In another embodiment, adjustingincludes adjusting one of the nominal substitution rate and the loadsubstitution description in response to the expected fuel flow rate andthe third amount of the liquid fuel.

According to another aspect, a system includes an engine outputdefinition module structured to operate a dual fuel engine at one of anincreased liquid fuel fraction and a 100% liquid fuel fraction, and todetermine an engine load value; a fuel energy definition modulestructured to determine an expected fuel flow rate in response to anominal substitution rate, a load substitution description, and theengine load value, where the expected fuel flow rate includes one of agaseous fuel rate and a resulting liquid fuel rate, and where the loadsubstitution description includes a replacement amount of gaseous fuelthat provides an amount of torque equivalent to a replaced amount of aliquid fuel; a fuel check module structured to operate the dual fuelengine at a partially substituted operating condition where a thirdamount of the liquid fuel is substituted with a fourth amount of thegaseous fuel; a fuel energy quality module structured to compare one of:the resulting liquid fuel rate to the expected fuel flow rate and aneffective gaseous fuel flow rate to the replacement amount of thegaseous fuel; and a fuel energy correction module structured to adjustthe nominal substitution rate in response to the comparing.

In one embodiment of the system, the dual fuel engine includes a firstgaseous fuel source providing the gaseous fuel and a second liquid fuelsource providing the liquid fuel. In another embodiment of the system,the engine output definition module is further structured to operate thedual fuel engine at an increased liquid fuel fraction by reducing agaseous fuel flow rate from a nominal gaseous fuel flow rate determinedaccording to the nominal substitution rate. In a refinement of thisembodiment, the engine output definition module is further structured toreduce the gaseous fuel flow rate from the nominal gaseous fuel flowrate by one of a predetermined amount and a detectable amount.

In another embodiment, the gaseous fuel includes at least one fuelselected from the fuels consisting of: well gas, field gas, nominallytreated well gas, nominally treated field gas, condensate, LPG, LNG,CBM, commercially available gas, and mixtures of these.

According to another aspect, a method includes operating a dual fuelengine on a first gaseous fuel amount that is less than the gaseous fuelamount indicated by a nominal substitution rate by a predeterminedamount, and determining an engine load value; determining an expectedfuel flow rate in response to a nominal substitution rate, a loadsubstitution description and the predetermined amount, where theexpected fuel flow rate includes one of a second gaseous fuel rate and aresulting liquid fuel rate, and where the load substitution descriptionincludes a replacement amount of gaseous fuel that provides an amount oftorque equivalent to a replaced amount of a liquid fuel; operating thedual fuel engine at a partially substituted operating condition where athird amount of the liquid fuel is substituted with a fourth amount ofthe gaseous fuel, and where the partially substituted operatingcondition includes a greater amount of the gaseous fuel than the firstgaseous fuel amount; comparing one of: the resulting liquid fuel rate tothe expected fuel flow rate and an effective gaseous fuel flow rate tothe replacement amount of the gaseous fuel, and adjusting the nominalsubstitution rate in response to the comparing.

According to another aspect, a method includes inducing a change in adual fuel engine to operate at a prescriptively reduced or eliminatedgas fuel fraction; determining a torque make up amount of liquid fuelutilized to maintain at least one of: engine speed, engine load, andengine power; determining an effective gas flow rate in response to thetorque make up amount of liquid fuel and the prescriptively reduced oreliminated gas fuel fraction; and adjusting at least one of a nominalsubstitution rate and a load substitution description in response to theeffective gas flow rate.

According to another aspect, a method includes determining a first workamount for an operating internal combustion engine; determining a firstheat dissipation amount for the operating internal combustion engine;determining a fuel energy amount for the operating internal combustionengine in response to a liquid fuel amount and a gaseous fuel amount;determining a gaseous fuel quality value in response to the fuel energyamount, the first heat dissipation amount, the first work amount, theliquid fuel amount, and the gaseous fuel amount; and adjusting at leastone of a nominal substitution rate and a load substitution descriptionin response to the gaseous fuel quality value.

In one embodiment, the method includes determining the fuel energyamount in response to determining the internal combustion engine isoperating in a nominal heat transfer environment. In a refinement ofthis embodiment, determining the internal combustion engine is operatingin a nominal heat transfer environment includes at least one operationselected from the operations consisting of: determining that an enginecoolant temperature is within a predetermined range (inclusive),determining that an ambient air temperature is within a predeterminedrange (inclusive), and determining that a vehicle speed is within apredetermined range (inclusive).

In another embodiment of the method, determining the heat dissipationamount includes determining an excess thermal energy amount present inan exhaust gas of the engine. In yet another embodiment of the method,determining the fuel energy amount includes performing a system energybalance, and defining a downstream boundary of the system at one ofupstream of a turbine and downstream of a turbine.

In yet another embodiment of the method, adjusting at least one of anominal substitution rate and a load substitution description includes:adjusting the at least one of the nominal substitution rate and the loadsubstitution description to compensate for an engine knock effect,adjusting the at least one of the nominal substitution rate and the loadsubstitution description to compensate for a fuel injector tiptemperature effect, and adjusting the at least one of the nominalsubstitution rate and the load substitution description to compensatefor an exhaust gas temperature effect.

In yet another aspect, a system includes a controller with an energydissipation module structured to determine a first work amount for anoperating internal combustion engine and a first heat dissipation amountfor the operating internal combustion engine, an energy generationmodule structured to determine a fuel energy amount for the operatinginternal combustion engine in response to a liquid fuel amount and agaseous fuel amount, a fuel quality determination module structured todetermine a gaseous fuel quality value in response to the fuel energyamount, the first heat dissipation amount, the first work amount, theliquid fuel amount, and the gaseous fuel amount, and a fuel energycorrection module structured to adjust at least one of a nominalsubstitution rate and a load substitution description in response to thegaseous fuel quality value.

In one embodiment, the system includes the internal combustion enginehaving a first gaseous fuel source providing the gaseous fuel amount anda second liquid fuel source providing the liquid fuel amount, and ameans for determining the internal combustion engine is operating in anominal heat transfer environment. In a refinement of this embodiment,the system includes a turbocharger having a turbine side disposed in anexhaust gas stream of the internal combustion engine, and the energydissipation module is further structured to define a downstream boundaryfor a system energy balance at an upstream side of the turbine. Inanother refinement of this embodiment, the system includes aturbocharger having a turbine side disposed in an exhaust gas stream ofthe internal combustion engine, and the energy dissipation module isfurther structured to define a downstream boundary for a system energybalance at a downstream side of the turbine.

According to another aspect, a method includes determining a gascomposition parameter for a gaseous fuel provided to a dual fuelinternal combustion engine, the gas composition parameter including atleast one parameter selected from the parameters consisting of: a fuelenergy content description and a knock tendency description, adjusting abase fueling recipe in response to the gas composition parameter, andproviding a first amount of the gaseous fuel and a second amount of aliquid fuel to the internal combustion engine in response to theadjusting the base fueling recipe.

In one refinement of this method, the gas composition parameter includesa fuel energy content description that indicates a fuel energy contentof the gaseous fuel is lower than a nominal fuel energy value, and theadjusting the base fueling recipe includes at least one operationselected from the operations consisting of: increasing an amount of thegaseous fuel provided to the engine, adjusting a load substitutiondescription where the load substitution description includes areplacement amount of the gaseous fuel that provides an amount of torqueequivalent to the replaced amount of the liquid fuel, adjusting anominal substitution rate of the gaseous fuel for the liquid fuel, andadjusting at least one of a target EGR rate and a target charge flowvalue.

According to another embodiment, the gas composition parameter includesa fuel energy content description that indicates a fuel energy contentof the gaseous fuel is higher than a nominal fuel energy value, andadjusting the base fueling recipe includes at least one operationselected from the operations consisting of: decreasing an amount of thegaseous fuel provided to the engine, adjusting a load substitutiondescription where the load substitution description includes areplacement amount of the gaseous fuel that provides an amount of torqueequivalent to the replaced amount of the liquid fuel, adjusting anominal substitution rate of the gaseous fuel for the liquid fuel, andadjusting at least one of a target EGR rate and a target charge flowvalue.

In another embodiment, the gas composition parameter includes a knocktendency description that indicates a methane number higher than anominal methane number, and adjusting the base fueling recipe includesat least one operation selected from the operations consisting of:adjusting a liquid fuel injection timing; adjusting a liquid fuelinjection pressure, adjusting at least one of a target EGR rate and atarget charge flow value, and adjusting a nominal substitution rate ofthe gaseous fuel for the liquid fuel.

In yet another embodiment, the gas composition parameter includes aknock tendency description that indicates a methane number lower than anominal methane number, and adjusting the base fueling recipe includesat least one operation selected from the operations consisting of:adjusting a liquid fuel injection timing, adjusting a liquid fuelinjection pressure, adjusting at least one of a target EGR rate and atarget charge flow value, and adjusting a nominal substitution rate ofthe gaseous fuel for the liquid fuel.

In another embodiment, the method includes, in response to determiningthe knock tendency description indicates at least one of an increasedknock tendency and a reduced methane number, performing at least oneoperation selected from the operations consisting of: retarding a liquidfuel injection timing, reducing a liquid fuel injection pressure,increasing a gaseous phase air-fuel-ratio by increasing a fresh air flowrate, and increasing a gaseous phase air-fuel-ratio by decreasing thefirst amount of the gaseous fuel.

According to another aspect, a system includes a controller thatincludes a gas composition definition module structured to determine agas composition parameter for a gaseous fuel provided to an internalcombustion engine, the gas composition parameter including at least oneparameter selected from the parameters consisting of: a fuel energycontent description and a knock tendency description. The controllerfurther includes a combustion management module structured to provide anadjusted base fueling recipe in response to the gas compositionparameter, the adjusted base fueling recipe including at least oneparameter selected from the parameters consisting of: a gaseous fuelsubstitution rate, an air-fuel-ratio, a liquid fuel injection timing, aliquid fuel injection pressure, a valve timing selection, an oxygenfraction value, an oxygen amount value, an EGR flow rate value, an EGRfraction value, an IMT value, an IMP value, a charge flow value, and acharge temperature value. The controller also includes an engine controlmodule structured to provide a first amount of the gaseous fuel and asecond amount of a liquid fuel to the internal combustion engine inresponse to the adjusted base fueling recipe.

In one embodiment of the system, the internal combustion engine includesa first gaseous fuel source providing the first amount of the gaseousfuel and a second liquid fuel source providing the second amount of theliquid fuel, and a means for providing an adjusted engine operation inresponse to the adjusted base fueling recipe.

According to another aspect, a system includes an internal combustionengine including a fuel system having a gaseous fuel source and a liquidfuel source, and the engine further includes a plurality of combustionchambers. A performance isolation device is structured to interpret afirst combustion performance indicator of a first one of the combustionchambers, where the first combustion performance indicator is at leastpartially isolated from the combustion performance of the entireplurality of combustion chambers. The system also includes a controllerincluding a performance check module structured to command the fuelsystem to provide only liquid fuel to the first one of the combustionchambers, and to provide both gaseous fuel and liquid fuel to theremaining combustion chambers. The controller also includes aperformance differentiation module structured to interpret the firstcombustion performance indicator and to interpret an aggregateperformance indicator, a gaseous fuel definition module structured todetermine a gas composition parameter in response to the firstcombustion performance indicator and the aggregate performanceindicator, and a composition response module structured to, in responseto the gas composition parameter, perform at least one operationselected from the operations consisting of: adjust a base fuelingrecipe, adjust a nominal substitution rate, adjust a load substitutiondescription where the load substitution description includes areplacement amount of the gaseous fuel that provides an amount of torqueequivalent to the replaced amount of the liquid fuel, and store the gascomposition parameter in a non-transient memory storage location.

In one embodiment, the performance isolation device includes at leastone device selected from the devices consisting of: a temperature sensorpositioned to determine an exhaust gas temperature of the first one ofthe combustion chambers, a temperature sensor positioned to determine anexhaust gas temperature of the plurality of combustion chambers,including preferentially weighting the temperature of the first one ofthe combustion chambers, a temperature sensor positioned to determine anin-cylinder temperature of the one of the combustion chambers, anaccelerometer structured to determine a torque contribution of the firstone of the combustion chambers, and a pressure sensor positioned todetermine an in-cylinder pressure of the one of the combustion chambers.

In another embodiment, the composition response module is furtherstructured to adjust the base fueling recipe by at least one operationselected from the operations consisting of: adjusting at least one of atarget EGR rate and a target charge flow value, adjusting a liquid fuelinjection timing, and adjusting a liquid fuel injection pressure.

In yet another embodiment, the aggregate performance indicator includesat least one of the following: a bulk exhaust gas temperature, anaverage combustion event torque contribution, a modeled combustion eventparameter, and a predetermined combustion event parameter stored in anon-transient memory location.

According to another aspect, an apparatus includes a performance checkmodule structured to command a fuel system to provide only liquid fuelto a first one of a plurality of combustion chambers, and to provideboth gaseous fuel and liquid fuel to the remaining combustion chambers;a performance differentiation module structured to interpret a firstcombustion performance indicator and to interpret an aggregateperformance indicator; a gaseous fuel definition module structured todetermine a gas composition parameter in response to the firstcombustion performance indicator and the aggregate performanceindicator; and a composition response module structured to, in responseto the gas composition parameter, perform at least one operationselected from the operations consisting of: adjust a base fuelingrecipe, adjust a nominal substitution rate, adjust a load substitutiondescription where the load substitution description includes areplacement amount of the gaseous fuel that provides an amount of torqueequivalent to the replaced amount of the liquid fuel, and store the gascomposition parameter in a non-transient memory storage location.

In one embodiment, the composition response module is further structuredto, in response to determining the gas composition parameter indicatesat least one of an increased knock tendency and a reduced methanenumber, perform at least one operation selected from the operationsconsisting of: retard a liquid fuel injection timing, reduce a liquidfuel injection pressure, increase a gaseous phase air-fuel-ratio byincreasing a fresh air flow rate, and increase a gaseous phaseair-fuel-ratio by decreasing an amount of the gaseous fuel.

According to another aspect, a system includes an internal combustionengine having a first cylinder and a second cylinder. The system alsoincludes a fuel system having a first fuel source including a dieselfuel and a second fuel system having a second fuel source including agaseous fuel, each of the first cylinder and the second cylinderoperationally coupled to both the first fuel system and the second fuelsystem. The system also includes a controller that includes an enginecondition module structured to interpret an engine operating value and afuel control module. The fuel control module is structured to provide,in response to the engine operating value, at least one first fuelsource command and at least one second fuel source command such that afirst ratio of the diesel fuel to the gaseous fuel in the first cylinder(d1:g1) is distinct from a second ratio of the diesel fuel to thegaseous fuel in the second cylinder (d2:g2).

In one embodiment, the engine operating value includes a fuel injectortip temperature value. In a refinement of this embodiment, the fuelcontrol module is further structured to increase the ratio d1:g1 toreduce the fuel injector tip temperature value for the injector tip inthe first cylinder. In a further refinement, the fuel control module isfurther structured to alternate increased diesel ratios betweencylinders to reduce the fuel injector tip temperature valuescorresponding to the injector tips in each of the various cylinders.

In another embodiment, the second fuel system includes one of gaseousport injection and gaseous direct injection, and the engine operatingvalue includes a gaseous injector failure value corresponding to thefirst cylinder, and the fuel control module is further structured tomodify the ratio d1:g1 in response to the gaseous injector failurevalue. In a refinement of this embodiment, the fuel control module isfurther structured to increase a diesel fueling amount to the firstcylinder in response to the gaseous injector failure value indicating agaseous fuel injector operationally coupled to the first cylinder isdelivering less than a scheduled fueling amount of gaseous fuel. Inanother refinement, the fuel control module is further structured todecrease a diesel fueling amount to the first cylinder in response tothe gaseous injector failure value indicating a gaseous fuel injectoroperationally coupled to the first cylinder is delivering greater than ascheduled fueling amount of gaseous fuel. In yet another refinement, thefuel control module is further structured to increase a gaseous fuelingamount in at least one cylinder of the internal combustion engine thatis not the first cylinder.

In another embodiment, the fuel control module is further structured toprovide the first fuel source command such that the first cylinder isfully fueled with diesel. In a refinement of this embodiment, the engineoperating value includes an emissions value. In a further refinement,the emissions value includes at least one value selected from the valuesconsisting of: an aftertreatment component regeneration request, anunburned hydrocarbons value, and an exhaust temperature value.

In another refinement of the previous embodiment, the system includes atransient detection module structured to provide the engine operatingvalue as a transient duty cycle value. In a further refinement, thetransient detection module is further structured to provide the engineoperating value by at least one operation selected from the operationsconsisting of: utilizing a high pass filtered load value of the engine,utilizing a derivative load value of the engine, utilizing a slope valueof moving average engine load values, accepting an operator inputindicating an upcoming transient, and interpreting a load schedule (e.g.a pump schedule) indicating an upcoming transient. In a furtherembodiment, the transient detection module is structured to interpret ageological formation schedule and operate the engine in response totransient conditions created by the geological formation. In a furtherembodiment, differential fuelling or substitution rates of gaseous fuelfor liquid fuel between cylinders and/or between cylinder banks of aduel fuel engine is performed in response to transient conditions.

In another aspect, a system includes a dual-fuel engine structured toselectably combust liquid fuel injected into a cylinder of the engineand gaseous fuel provided to the cylinder with the intake charge. Thesystem also includes an electronically controllable valve structured tocontrol a flow of the gaseous fuel and an electronic controller. Thecontroller is structured to determine a parameter representative of agaseous fuel quality based upon at least one of a first value externallyinput into the system and a second value determined by the electroniccontroller without external input to the system, determine asubstitution parameter for substitution of gaseous fuel for liquid fuelbased upon an engine load value, an intake manifold temperature value,and the parameter representative of the gaseous fuel quality, andcontrol the electronically controllable valve to control the flow of thegaseous fuel based upon the substitution parameter.

In one embodiment, the substitution parameter is a substitution rate. Inanother embodiment, the controller utilizes the engine load value, theintake manifold temperature value, and the gaseous fuel quality value todetermine a target substitution rate from a set of tables. In a furtherembodiment, the parameter representative of the gaseous fuel qualitycomprises a methane number (MN).

In yet another embodiment, the controller is structured to selectablydetermine the parameter representative of the gaseous fuel quality basedupon either the first value or the second value. In a refinement of thisembodiment, the controller is structured to determine the second valuebased upon engine knock information. In a further refinement, the engineknock information includes a number of knock events and a knock eventmagnitude. In yet a further refinement, the controller is structured toreduce the substitution parameter based upon either the number of knockevents exceeding a first limit or the knock event magnitude exceeding asecond limit. In another refinement, the controller is structured toincrease the gaseous fuel quality value up to a maximum value until theengine knock information meets a predetermined criterion. In a furtherrefinement, the controller is structured to decrease the substitutionparameter if the engine knock information meets the predeterminedcriterion and to later resume increasing the value of the gaseous fuelquality.

According to another aspect, a method includes operating a dual-fuelengine structured to selectably combust a combination of liquid fuelinjected into a cylinder of the engine and gaseous fuel provided to thecylinder. The system includes an actuator structured to control flow ofthe gaseous fuel and a controller structured to control the actuator.The method further includes operating the controller to determine agaseous fuel quality based upon at least one of a first value input intothe system by an operator and a second value determined by theelectronic controller, determine a target substitution value forsubstitution of gaseous fuel for liquid fuel based upon an engine load,an intake manifold temperature, and the gaseous fuel quality, andcontrol the actuator to control the flow of the gaseous fuel based uponthe target substitution value.

In one embodiment, the substitution value is a substitution quantity. Inanother embodiment, the controller utilizes the engine load, the intakemanifold temperature, and the determined gaseous fuel quality as inputsto a set of look-up tables to determine the target substitution value.In a refinement of this embodiment, the controller interpolates betweendiscrete table values to determine the target substitution value. In yetanother embodiment, the determined gaseous fuel quality comprises amethane number (MN).

In yet another embodiment, the controller is structured to determine thegaseous fuel quality based upon either the first value or the secondvalue, and the controller is structured to determine the second valuebased on engine knock information. In a refinement of this embodiment,the engine knock information includes a knock event counter value. In afurther refinement, the controller is structured to reduce thesubstitution value based upon the knock event counter value exceedingfirst limit.

In another embodiment, the controller is structured to increase thedetermined gaseous fuel quality up to a predetermined value until theengine knock information meets a predetermined criterion. In arefinement of this embodiment, the controller is structured to stopincreasing or decrease the determined gaseous fuel quality when theengine knock information meets the predetermined criterion and to laterresume increasing the determined gaseous fuel quality.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly certain exemplary embodiments have been shown and described. Thoseskilled in the art will appreciate that many modifications are possiblein the example embodiments without materially departing from thisinvention.

Accordingly, all such modifications are intended to be included withinthe scope of this disclosure as defined in the following claims.

In reading the claims, it is intended that when words such as “a,” “an,”“at least one,” or “at least one portion” are used there is no intentionto limit the claim to only one item unless specifically stated to thecontrary in the claim. When the language “at least a portion” and/or “aportion” is used the item can include a portion and/or the entire itemunless specifically stated to the contrary.

What is claimed is:
 1. A method, comprising: determining an expectedknock value for a gaseous fuel in a dual fuel engine; determining acurrent knock value for the gaseous fuel in a dual fuel engine;determining an adjusted substitution rate for the gaseous fuel inresponse to comparing the expected knock value and the current knockvalue; and fueling the dual fuel engine with an amount of the gaseousfuel in response to the adjusted substitution rate, wherein thedetermining the current knock value comprises fueling the dual fuelengine with an amount of the gaseous fuel that is greater than arequested amount of the gaseous fuel, wherein the requested amount ofthe gaseous fuel comprises at least one of an amount of the gaseous fuelindicated by a nominal substitution rate and an amount of the gaseousfuel indicated by a substitution rate in use before the adjustedsubstitution rate.
 2. The method of claim 1, wherein the determining thecurrent knock value comprises observing a knock event, and determiningthat a current substitution rate is not expected to incur the knockevent, wherein the determining the current knock value further comprisesreducing a substitution rate until the knock event is no longerobserved, and determining the reduced substitution rate which does notcause the knock event.
 3. The method of claim 1, further comprisingconsidering an operating region of the engine, and associating dataregarding the expected knock value, the current knock value, a nominalsubstitution rate, a current substitution rate, and the adjustedsubstitution rate with the operating region of the engine at the timethe data is utilized.
 4. The method of claim 3, wherein the operatingregion of the engine comprises at least one parameter selected from theparameters consisting of: an engine speed, an engine load, a charge flowrate, an air flow rate, an intake manifold temperature, an exhaustmanifold temperature, an intake manifold pressure, an exhaust manifoldtemperature, a recirculated exhaust gas temperature, an oxygen amount,and an oxygen fraction.
 5. The method of claim 1, wherein thedetermining the adjusted substitution rate for the gaseous fuelcomprises determining an effective fuel substitution rate for thegaseous fuel, the effective fuel substitution rate for the gaseous fuelcomprising a first amount of gaseous fuel that provides an amount ofeffective torque equivalent to a second amount of a liquid fuel, whereinthe effective fuel substitution rate is distinct from a nominal fuelsubstitution rate.
 6. A system, comprising: a dual fuel engine operablewith a liquid fuel and a gaseous fuel; and a controller operably coupledto the engine, wherein the controller is configured to determine anexpected knock value for the gaseous fuel in the dual fuel engine and acurrent knock value for the gaseous fuel in the dual fuel engine, thecontroller further being configured to determine an adjustedsubstitution rate for the gaseous fuel in response to comparing theexpected knock value and the current knock value, and to command fuelingfor the dual fuel engine in response to the adjusted substitution rate,and wherein the controller is configured to determine the current knockvalue in response to the dual fuel engine being fueled with an amount ofthe gaseous fuel that is greater than a requested amount of the gaseousfuel.
 7. The system of claim 6, further comprising the dual fuel enginehaving a first gaseous fuel source providing the gaseous fuel and asecond liquid fuel source providing a liquid fuel.
 8. The system ofclaim 7, further comprising: a means for determining the expected knockvalue; a means for determining the current knock value; and a means forassociating the current knock value and the expected knock value,wherein the current knock value is determined in a time domain and theexpected knock value is determined outside the time domain in which thecurrent knock value is determined.
 9. The system of claim 8, wherein themeans for associating the current knock value and the expected knockvalue further comprises a means for associating the current knock valueand the expected knock value by at least one parameter selected from theparameters consisting of: an engine speed, an engine load, a charge flowrate, an air flow rate, an intake manifold temperature, an exhaustmanifold temperature, an intake manifold pressure, an exhaust manifoldpressure, a recirculated exhaust gas temperature, an oxygen amount, andan oxygen fraction.
 10. The method of claim 1, wherein the current knockvalue is determined in a time domain and the expected knock value isdetermined outside the time domain in which the current knock value isdetermined.
 11. The system of claim 6, wherein the requested amount ofthe gaseous fuel comprises at least one of an amount of the gaseous fuelindicated by a nominal substitution rate and an amount of the gaseousfuel indicated by a substitution rate in use before the adjustedsubstitution rate.